The present invention generally relates to fuel systems for an internal combustion engine. More particularly, the present invention relates to a multi-fuel system for an internal combustion engine that utilizes both diesel and natural gas.
It is estimated that there are currently three hundred million vehicles on America's roads. Every day, the average American spends almost an hour driving in a car. Additionally, approximately seventy percent of goods that are shipped in America travel on commercial vehicles. Clearly, automobiles are an integral part of everyday life in America. The same is true for most countries around the world. The world's dependence on automobiles creates a similar dependence on fuel sources to power these automobiles. Most vehicles on the road today are fueled by gasoline or diesel fuel. Most commercial vehicles are fueled by diesel fuel.
The reliance on fossil fuels creates a host of problems. Diesel fuel prices fluctuate on a daily basis, but there is a definite upward trend in fuel pricing. There are no indicators to suggest that these fuel prices will go down in the foreseeable future. The air pollution problems inherent in the operation of gasoline fueled and diesel oil fueled internal combustion engines are well known. These air pollutants include carbon monoxide, nitrogen dioxide, particulate matter, ozone, sulfur dioxide and lead. All these pollutants are known sources of a wide variety of health problems in humans, as well as ozone depletion and acid rain in the environment. Many speculate that air pollution is causing the gradual and irreversible warming of the globe.
For these reasons, various emission control devices are presently in use, and may be required by federal regulations in order to reduce the amount of pollutants discharged in the atmosphere by internal combustion engines. These emission control devices are in response to various Air Quality Standards set by the Environmental Protection Agency (EPA), including the Clean Air Act. Individual states also have their own environmental protection regulations and methods of enforcement. California's Air Resources Board (CARB) is the strictest regulatory body concerned with pollution in the country. The emissions standards set by CARB are stricter than the federal EPA requirements, specifically with regard to hydrocarbon and nitrogen oxide emissions, which become smog. Currently, sixteen other states have adopted, or are in the process of adopting, California's strict emissions standards.
Emission control devices, however, only remove a portion of the pollutants and are subject to deterioration with the passage of time. Also, they often hinder engines from operating at peak efficiencies. Such emission control devices also are somewhat limited in their ability to remove pollutants, and increase the costs of the automobiles significantly.
Discharge or burning of blow-by gas also contributes to emissions. In a diesel powered engine, oil is used to lubricate the crankshaft and connecting rod bearings. The crankcase is mainly filled with air and oil. It is the intake manifold that receives and mixes fuel and air from separate sources. The fuel/air mixture in the intake manifold is drawn into the combustion chamber where it is ignited by a sparkplug, or as a result of compression in the combustion chamber due to the movement of the piston shaft. Although piston rings, disposed around the outer diameter of the pistons within the piston cylinder, are intended to seal off from the crankcase the unburned and burned fuel and air injected into the combustion chamber, the piston rings are unable to completely seal off the piston cylinder. Thus, waste gas enters the crankcase, which is commonly called “blow-by” gas.
Blow-by gasses mainly consist of contaminants such as hydrocarbons (unburned fuel), carbon dioxide and/or water vapor, all of which are harmful to the engine crankcase. The trapping of blow-by gasses in the crankcase allows the contaminants to condense and accumulate over time in the engine crankcase. Condensed contaminants form corrosive acids and sludge in the interior of the crankcase. This decreases the ability of the engine oil in the crankcase to lubricate the cylinder and crankshaft. The degraded oil that fails to properly lubricate the crankshaft components can be a factor in increased wear and tear in the engine, as well as poor engine performance.
Crankcase ventilation systems have been developed to expel blow-by gasses out of a positive crankcase ventilation (PCV) valve and into the intake manifold to be re-burned. However, such blow-by gasses removed from the crankcase often contain relatively high levels of lubricating oil and the like, which are introduced into the air intake manifold and thus into the combustion chamber, which increases the pollution generated by the vehicle.
These issues are especially problematic in diesel engines as diesel engines burn diesel fuel which is much more oily and heavy than gasoline. Thus, the blow-by gas produced by the crankcase of the diesel engine is much more oily and heavy than gasoline blow-by gas. Of course, the burning of such diesel blow-by gas creates even a greater pollution concern.
Recently, there have been found vast sources of natural gas within the United States. Natural gas is also sometimes used as a fuel for internal combustion engines. It has the capability of producing less combustion pollutants and decreasing engine operating costs without complex emission control devices. Its use is anticipated to reduce the rate of world fossil fuel consumption.
Since the current transportation infrastructure does not include large numbers of widely dispersed retail suppliers of natural gas for vehicles, it has been impractical to produce vehicles that are fueled solely by gaseous fuels like natural gas due to range limitations. Instead, it is more practical to equip vehicles with a supply of both a liquid fuel, such as diesel fuel, and an auxiliary supply of gaseous fuel such as natural gas.
Accordingly, there is a continuing need for a system which is capable of burning not only diesel fuel, but diesel fuel combined with natural gas so as to lessen the emissions of the diesel combustion engine. What is further needed is such a system that does so with as little retrofitting as possible to the existing fuel intake systems and configuration, in order to lessen the complexity and the cost of the system and also to enable existing diesel engines to be retrofitted. What is also needed is such a system that filters the blow-by gas of the diesel engine crankcase, so as to maintain a clean and filtered lubricating oil within the crankcase, while lessening the environmental impact of blow-by gasses that are introduced into the combustion chamber. The present invention fulfills these needs, and provides other related advantages.